1. Field of the Invention
This invention relates to pneumatically operated valves for controlling the flow of high pressure gases and more particularly to such valves which can be operated by commercially available pneumatic pressures at or below 100 psig. Such valves are particularly suitable as compressed gas cylinder valves.
2. Background Information
Our commonly owned U.S. patent application Ser. No. 06/938,824 filed on Dec. 8, 1986 now U.S. Pat. No. 4,706,929, discloses a pneumatically operated valve particularly suitable for use with compressed gas cylinders. The pneumatic actuator in that valve is designed for interchangeable use with the common manual actuators which have been in service for many years. That pneumatic actuator includes a cup shaped housing which screws into the conventional valve body. A valve stem extension protrudes into the housing and bears against a piston which is biased against the valve stem extension by a stack of disc springs. The force applied by the disc springs to the valve stem extension through the piston, biases the valve to the closed position. Pneumatic pressure introduced into the actuator applies a force to the piston to compress the disc springs. This allows a valve spring to move the valve stem to the open position.
The gas cylinders with which such pneumatically operated valves are used are typically charged to pressures as high as 2000 psig. To assure that the gas cylinder does not leak at such high pressures, a substantial force must be generated by the disc springs. This is particularly important where such gas cylinders are used to store highly toxic gases used for example in the semiconductor industry. It is also desirable that the actuator be of a size which fits under the conventional transport cap used during shipment and storage of the gas cylinders. Such constraints have necessitated that a pneumatic pressure of about 160 PSI be used to operate the pneumatic actuator. Since the typical house pressure found in industry is about 90 PSI, a separate pneumatic system or intensifiers are needed to operate our present pneumatically actuated cylinder valve.
Accordingly, it is a primary object of the invention to provide a pneumatically actuated cylinder valve and an actuator therefore which can be operated at normally available house pressures.
It is another important object of the invention to provide such a valve and an actuator which will ensure valve shut off on a full gas cylinder.
It is another important object of the invention to provide such a valve and actuator which can be used interchangeably with the commonly available manual actuators and which will fit under the conventional transport caps.
It is also an object of the invention to provide such a valve and actuator which are durable and reliable and which can be manufactured and assembled easily and economically.